Rev counter stopped.

[tonygunton]

Having just travelled 100 plus miles on final return to home the rev counter packed up abruptly. This was the first long run of the season and was it working without a hitch until it just stopped. Had been recording between 4000 and 4750 rpm for the last 30 miles. Is this a cable failure given the sudden nature of the problem or something more serious? Any thoughts gratefully received.

[Keith Clements]

Pretty easy to tell if cable failure.
Unscrew cable from back of gauge and see if you can turn it, then start engine and see if it turns.
Yes there are many other reasons why the rev counter may not work.
If the cable is turning then check it was screwed up properly into the gauge.
If it is then take out gauge and look inside it. Or perhaps test with a variable speed drill.
If the cable is not turning make sure the gearbox on back of dynamo is properly attached.

[Srenner]

All the test KC recommends are good. A bad cable usually is indicated by a waving needle as the cable grabs and releases, but that's not mentioned in your post.

The gearbox has a small u-joint and the visible part is the keyed shaft that inserts into the dynamo. Of the half dozen I have played with, all had developed some wear and up to total failure at the pivot pin. If the counter was operating smoothly and suddenly failed, that is the first thing I would check.

As noted before, could be many other things as well.